In recent years, such a vehicle as an economical-running vehicle, for example a hybrid car, in which an operation of an internal combustion engine is temporarily stopped at a vehicle stop in case of waiting for a change of a traffic lamp, is realized, in view of an environment protection, an improvement of a fuel consumption ratio and so on. And a demand for such vehicles is increasing.
In an air conditioning system for a vehicle, a compressor for a refrigerating cycle is operated by an internal combustion engine for the vehicle. As a result, the operation of the compressor is likewise temporarily stopped whenever the operation of the engine is stopped in case of waiting for a change of a traffic lamp. Then, a temperature at a cooling evaporator will be increased, and thereby a temperature of air to be blown into a vehicle passenger room will be increased. Accordingly, a feeling of a cooling operation for the passenger would become worse.
A demand for an air conditioning system of a cool storage type has been therefore increased, wherein the air conditioning system comprises a cool storage means for storing cooling energy during an operation of an engine (and a compressor) and a cooling operation is continued with the stored cooling energy during the operation of the engine and the compressor is stopped.
The air conditioning system of this kind is known in the art, for example as disclosed in Japanese Patent Publication No. 2000-313226. FIG. 22 is a schematic view showing the air conditioning system corresponding to that shown in the above Japanese Patent Publication. In a refrigerating cycle shown in FIG. 22, a compressor 1 is driven by an engine of a vehicle, and a cool storage heat exchanger 40 containing therein cool storage material 40a is connected in parallel with an evaporator 8.
An electromagnetic valve 41 is opened during the engine and the compressor 1 are operated, so that low pressure refrigerant depressurized by an expansion valve 7 flows in parallel into the evaporator 8 and the cool storage heat exchanger 40, to cool down the cool storage material 40a and store the cooling energy in the cool storage material 40a. When the engine is stopped and thereby the compressor stops its operation, an electrically driven pump 42 is operated to circulate the refrigerant in a closed cycle comprising a liquid storing tank 43, the electromagnetic valve 41, the electrically driven pump 42, the cool storage heat exchanger 40 and the evaporator 8.
The gas-phase refrigerant evaporated in the evaporator 8 is condensed by the cooling energy of the cool storage material 40a, and the condensed liquid-phase refrigerant is supplied to the evaporator 8, so that a cooling operation by the air conditioning system can be continued even during the compressor operation is stopped.
The electrically driven pump 42 sucks the liquid-phase refrigerant from the liquid storing tank 43, shortly after the engine operation is stopped, namely shortly after the cooling operation by the cooling energy of the cool storage heat exchanger 40 has started. Since the electrically driven pump 42 is filled with the liquid-phase refrigerant at the starting period of the pump, a lost motion of the electrically driven pump 42 can be avoided.
According to another prior art, as disclosed in Japanese Patent Publication No. 2004-51077 (which has been filed by the same applicant to the present invention), a cool storage heat exchanger 11, a liquid storing tank 10, an electrically driven pump 42 and a check valve 18 are connected as shown in FIGS. 23 and 24, and those components are arranged in a single tank designated by a two-dot-chain lines in those drawings, so that the air conditioning system can be easily installed in a vehicle.
In the air conditioning systems shown in FIGS. 23 and 24, the cool storage material 11a filled in the cool storage heat exchanger 11 is cooled down by the low pressure and low temperature refrigerant depressurized and expanded by an expansion valve 7 or by an orifice 70 and thereby the cooling energy is stored in the cool storage material 11a. When the engine and the compressor are stopped, the electrically driven pump 42 is operated to supply the cooled down refrigerant from the cool storage heat exchanger 11 to an evaporator 8, so that the cooling operation by the air conditioning system is continued. Reference numerals in FIGS. 23 and 24, which are not explained here, correspond to those elements or components explained below for the embodiments of the present invention.
In the above described prior art, the electrically driven pump, in which a mechanical pump is driven by an electric motor, is used for circulating the refrigerant. And thereby, it has a disadvantage in that a manufacturing cost is increased. Furthermore, there are following disadvantages, in the case that the electrically driven pump would be installed within the liquid refrigerant storing tank to improve an installing process of the air conditioning system into a vehicle:
(1) Since a liquid pump, such as a mechanical pump driven by an electric motor, can not generally pump out gas-phase fluid, the liquid pump must be located in a gas-liquid separating tank in such a manner that the liquid-phase fluid (refrigerant in this case) can be always predominantly supplied to the liquid pump. As a result, the manufacturing cost is increased and an additional space for the gas-liquid separating tank is necessary.
(2) Since the electric motor is used for driving the mechanical pump, the electric wires for supplying electric power to the electric motor are necessary, wherein the electric wires connect the outside electrical power source with the electric motor disposed within the liquid storing tank. As a result, the wires must be electrically insulated from the tank and the tank must be hermetically sealed because of the refrigerant therein. The manufacturing cost is thereby further increased.
(3) The electric motor must be disassembled from the liquid storing tank, in the case that brushes will be replaced by new ones due to the wear. The refrigerant must be removed from the refrigerating cycle for such replacement, and the refrigerant must be filled again into the refrigerating cycle after the replacement is completed. As a result, a maintenance fee is increased.